Don't mention Postgres roles, just say users

roles/matrix-postgres/templates/init-additional-db-user-and-role.sql.j2

@@ -4,7 +4,7 @@ DO $$
 BEGIN
   CREATE USER {{ additional_db.username }};
   EXCEPTION WHEN DUPLICATE_OBJECT THEN
-  RAISE NOTICE 'not creating role {{ additional_db.username }}, since it already exists';
+  RAISE NOTICE 'not creating user {{ additional_db.username }}, since it already exists';
 END
 $$;